These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
I Am Not Shazam: The heroine's name is Yuko, not Valis, in case you did not know.
That One Boss: The third game, the boss of the first level after finding Nazetti. Raining boulders, an attack that goes across the whole screen, and, of course, an absurd amount of health.
In the first game, the Twin-headed lightning dragon boss called Voldes, the Lord of Thunder. Naturally, Voldes gets annoying really fast due to the lightning spell. And then you fight Reiko, who can take away 48% of your health in a single spell cast (said spell is considerably weaker in your hands). The only way to dodge it is with a frame-perfect spell casting. The Final Boss is much easier due to not having a spell that hits the entire screen.